Gamma interferon (IFN-γ) and tumor necrosis factor-alpha (TNF-α) have been implicated in the development, exacerbation and/or recurrence of numerous autoimmune conditions. For example, both IFN-γ and TNF-α have been associated with the course of multiple sclerosis [Choflon et al., Eur. Cytokine Netw. 3(6), 1992, pp. 523-531; Steinman, Scientific American, September 1993, pp. 107-114; Hofman et al., J. Exp. Med. 170, 1989, pp. 607-612; Panitch et al., Neurology, 37, 1987, pp. 1097-1102] and Type-I diabetes (insulin-dependent diabetes meals, IDDM) [Castano et al., Annu. Rev. Immunol. 8, 1990, pp. 647-679; Campbell et al., J. Clin. Invest. 87, 1991, pp. 739-742]. While TNF-α has been found to promote development of rheumatoid arthritis [Feldmann et al., Progress in Growth Factor Research, 4, 1992, pp. 247-255], administration of IFN-γ has been linked to improvements in arthritic subjects [Veys et al., J. Rheumatology; 15(4), 1988, pp. 570-574]. Studies have also demonstrated the involvement of IFN-γ in the autoimmune diseases processes associated with systemic lupus erythematosus (SLE) [Funauchi et al., Tohoku J. Exp. Med., 164, 1991, pp. 259-267; Bankhurst, J. Rheumatology, 14(supp. 13), 1987, pp. 63-67], autoimmune thyroiditis [Tang et al., Eur. J. Immunol. 23, 1993, pp. 275-278], and autoimmune inflammatory eye disease (e.g., autoimmune uveoretinitis) [Charteris et al., Immunology 75, 1992, pp. 463-467]. Development of autoimmune pulmonary inflammation [Deguchi et al., Clin. Exp. Immunol. 85, 1991, pp. 392-395] and Guillain-Barre syndrome [Baron et al., Proc. Natl. Acad. Sci. USA 90, 1993, pp. 4414-4418] have also been tied to TNF-α activity.
Interleukin-12 (IL-12) is a heterodimeric cytokine which was originally identified as a factor which induces IFN-γ from T cells and natural killer cells as set forth in PCT/US91/06332, published Apr. 2, 1992. PCT/US91/06332 refers to IL-12 as Natural Killer Cell Stimulating Factor or NKSF. EP 433827, published Jun. 26, 1991 discloses IL-12 as a cytotoxic lymphocyte maturation factor (CLMF). IL-12 also stimulates natural killer cells in vitro by increasing their ability to lyse target cells at a level comparable to that obtained with IFN-α and IL-2, well-known activators of natural killer cells' cytotoxic activity. Additional in vitro activities of IL-12 which have been identified include induction of TNF-α; induction of T cell proliferation as a co-stimulant; suppression of IL-2 induced proliferation of natural killer blasts; suppression of IL-2 induced proliferation of T cell receptor-γδ-positive cells; promotion of Th1 T cell differentiation from progenitors; enhancement of Th1, but not Th2 proliferation; enhancement of T cell cytolytic activity; enhancement of cytotoxic lymphocyte generation; enhancement of natural killer and natural killer blast cytolytic activity; ex vivo enhancement of natural killer activity in peripheral blood mononuclear cells of IL-2-treated patients; induction of adhesion molecules on natural killer cells; induction of perforin and granzyme B mRNAs in natural killer blasts; induction of IL-2 receptor subunits (p55, p75) on natural killer cells; suppression of IgE synthesis by IFN-γ-dependent and independent mechanisms; modulation of T cell development in fetal thymic organ cultures; and synergy with kit ligand to promote growth of myeloid and B cell progenitors. The known in vivo activities of IL-12 include induction of IFN-γ; enhancement of natural killer cell activity in spleen, liver, lungs and peritoneal cavity; enhancement of generation of alto-specific cytotoxic lymphocytes; induction of extramedullary hematopoiesis in mouse spleen; reversible suppression of hematopoiesis in bone marrow; reversible induction of anemia, lymphopenia, and neutropenia in mice; suppression of anti-IgD induced IgE, IgG1, and IL-4 expression; increased survival in SCID mice treated with Toxoplasma gondii; cure of leishmaniasis in susceptible strains of mice; decreased bioburden in cryptococcoses model; suppression of tumor growth; and promotion of immunity to tumor cells. IL-12 is also induced in vivo in the shwarzman reaction model of septic shock.
Although IL-12 can induce production of IFN-γ and TNF-α in vivo, the relationship of in vivo levels of IL-12 to autoimmune diseases which are affected by levels of IFN-γ and TNF-α has not been established. Furthermore, the effects of administration of IL-12 or antagonists of endogenous IL-12 (such as anti-IL-12 antibodies) on autoimmune diseases associated with induction of IFN-γ or TNF-α have not been examined.